Various types of positioning systems which employ alternating electromagnetic fields are known. The following U.S. Patents and foreign patent documents are believed to represent the state of the art for positioning systems:
U.S. Pat. Nos. 4,054,881 and 4,314,251 to Raab; U.S. Pat. Nos. 4,622,644, 4,642,786, 5,742,394, 5,744,953, 5,767,669, 5,831,260 and 5,953,683 to Hansen; U.S. Pat. No. 4,737,794 to Jones; U.S. Pat. Nos. 4,613,866, 4,945,305 and 4,849,692 to Blood; U.S. Pat. Nos. 3,868,565, 3,983,474, 4,017,858, 4,298,874 and 4,742,356 to Kuipers; U.S. Pat. Nos. 5,168,222 and 5,172,056 to Volsin et al; U.S. Pat. No. 5,0170,172 to Weinstein; U.S. Pat. Nos. 5,453,686 and 5,640,170 to Anderson; U.S. Pat. No. 5,767,960 to Orman; U.S. Pat. No. 5,600,330 to Blood; U.S. Pat. No. 5,307,072 to Jones; U.S. Pat. No. 4,710,708 to Rorden; U.S. Pat. No. 4,346,384 to Raab; U.S. Pat. No. 4,328,548 to Crow; U.S. Pat. No. 5,558,091 to Acker; U.S. Pat. No. 5,592,939 to Martinelli; U.S. Pat. No. 6,073,043 to Schnieder; U.S. Pat. No. 3,644,825 to Davis; U.S. Pat. No. 5,377,678 to Dumoulin; U.S. Pat. Nos. 4,287,809 and 4,394,831 to Egli; U.S. Pat. No. 4,396,885 to Constant WO 96/05768 to Ben-Haim and WO 94/04938 to Bladen;
U.S. Pat. No. 4,710,708 to Rorden describes a positioning system which employs only one electromagnetic coil.
A description of accelerometer technology may be found in Capacitive Sensors, L. K. Baxter, 1998 ISBN 0-7803-5351-X;
U.S. Pat. No. 5,592,401 to Kramer, U.S. Pat. No. 5,657,226 to Shin, U.S. Pat. No. 5,615,116 to Gudat, U.S. Pat. No. 5,615,132 to Horton, U.S. Pat. No. 5,956,250 to Gudat, U.S. Pat. No. 5,902,351 to Streit, U.S. Pat. No. 5,991,692 to Spencer, U.S. Pat. No. 4,506,979 to Rogers, U.S. Pat. No. 5,051,751 to Gray and U.S. Pat. No. 5,930,741 to Kramer, all describe positioning systems which may employ Kalman filtering and acceleration measurements.
Phase Locked Loop technology is described in “Phase locked loop: simulation and applications”, by Roland E. Best, McGraw-Hill Book Company, ISBN 0070060517.
The theory of non-linear filtering and its applications is discussed in:
H. J. Kushner, “Approximations to Optimal Nonlinear Filters”. IEEE Trans. A.C., Vol. AC-12, No. 5, October 1967;
A. Gelb, J. F. Kaspar, Jr., R. A. Nash, Jr., C. E. Price, and A. A. Southerland, Jr., “Applied Optimal Estimation”, M.I.T. Press, Cambridge, Mass., 1974;
B. D. O. Anderson, and J. B. Moore, “Optimal Filtering”, Prentice-Hall, Englewood Cliffs, N.J., 1979;
A. H. Jazwinski, “Stochastic Processes and Filtering Theory”, Academic Press, New York, 1971; and
M. S. Grewal, and A. P. Andrews, “Kalman Filtering”, Prentice-Hall, Upper Saddle River, N.J., 1993.
The Electromagnetic field equation laws are discussed in:
J. D. Jackson, “Classical Electrodynamics”, John Wiley & Sons, New York, N.Y., 1975.
The application of Extended Kalman filters (EKF) to tracking in the context of radar is discussed, for example, in U.S. Pat. Nos. 5,075,694, 4,179,696, 3,952,304 and 3,935,572. Other tracking systems are discussed, for example, in U.S. Pat. Nos. 5,095,467 and 4,855,932.
The Kalman filter is a standard tool for “data fusion” of different sensors. In U.S. Pat. No. 5,416,712, Global Positioning System (GPS) signals and dead reckoning are combined by a Kalman filter, where the gyro bias is also calibrated. In U.S. Pat. No. 5,645,077 automatic drift compensation is discussed.
Reference is also made to positioning and tracking systems described in the following US patent and patent applications assigned to the assignee of the present invention, which are herein incorporated each in its entirety, by reference. U.S. Pat. No. 6,141,293 to Moriya at el.; U.S. patent application Ser. No. 09/345,189 entitled “A system and method for three dimensional positioning and tracking”, filed on Jun. 30, 1999 to Moriya and Itzkovich; U.S. patent application Ser. No. 09/384,314 entitled “A localization and tracking system”, filed on Aug. 27, 1999 to Moriya and Albeck; and U.S. patent application Ser. No. 09/503,436 entitled “A system for three dimensional positioning and tracking with dynamic range extension”, filed on Feb. 14, 2000 to Moriya.
The disclosures of all publications mentioned in the specification are hereby incorporated in their entirety by reference.